The present invention relates to a light emitting apparatus constituted so that infrared rays and visible rays can be simultaneously emitted.
In various photoelectric sensors such as, for instance, a photoelectric switch, a well-known infrared light emitting diode is generally used as its light source. As the reasons for the use of infrared light emitting diodes as light source in the field of photoelectric sensors, such facts can be enumerated as silicon dope and gallium-arsenic infrared light emitting diodes of which light emission efficiency is very excellent can be obtained at a very low price, infrared rays are selected for the purpose of performing detection without being affected by ambient natural rays, and the loss of infrared rays in an optical transmission route such as optical fiber, etc. is respectively small, etc.
However, one serious drawback of a photoelectric sensor using infrared light emitting diodes is that infrared light which is its measuring light, is not visible to the eyes of man. When a photoelectric sensor is acutally used, in many cases, it becomes necessary to confirm that its measuring light (infrared rays) is emitted or not, but in the case of infrared rays, this is not possible. In installing a photoelectric sensor to an object of measurement, it is also necessary to finely adjust the position of the object in relation to its measuring light, therefore a visible measuring light is convenient in such a case.
From such a point of view, the appearance of a socalled double color light emitting diode which is capable of simultaneously emitting a visible ray together with infrared rays is awaited. However, conventionally such a double color lihgt emititng diode has not been developed yet. In the field of visible light emitting diode, such diodes that are capable of simultaneously emitting multicolor lights such as green and red or green, orange and red, have already been put into practical use. However, a light emitting diode capable of simultaneously emitting infrared ray and visible ray has not been developed yet.